One of the problems associated with advancing magnetic recording technology is the interconnect between the write electronics and the writer and/or reader located on the slider. Conventional interconnects are typically 1-2 inches long and are often fabricated from polyimide materials containing imbedded circuit traces. The interconnect typically carries the write current pattern and readback signal and is physically attached to the suspension, which can act like an isolated ground plane for part of the interconnect length, or can be electrically connected to the suspension, and is therefore part of the actual circuit path. Interconnect designs, which are shorter and have ground planes, have been advanced as possible solutions for increasing interconnect bandwidth to stage higher data rate magnetic recording. However, the bandwidth capabilities of existing silicon-based write drivers are likely to limit the data rate transmission to a few Gbits/sec. Furthermore, the mechanical constraints associated with conventional interconnects, such as flex-on-suspension (FOS), are likely to contribute to the limitations of conventional data rate transmission. Typical FOS leads are capable of delivering electrical waveforms to the writer at the limited recording frequencies of from about 0.1 to 3.0 GHz. However, there are no proven methods capable of extending recording bandwidths to the frequency range of from about 5 GHz to about 10 GHz. Furthermore, there are no proven methods capable of extending recording bandwidths to THz frequencies.
A possible solution advanced for increasing interconnect bandwidth to stage higher data rate magnetic recording includes moving the write driver out onto the suspension system to physically move the driver output currents closer to the recording head thereby reducing the impact of the bandwidth of the FOS. However, moving the write driver onto the suspension poses significant challenges, for example, putting a silicon interconnect package out onto a suspension requires substantial heat sinking to dissipate the heat generated by the high current preamp chip. As a result, present efforts to extend recording data rates have focused on evolving the FOS bandwidth via a distributed transmission line model, where the preamp is adjusted to match measured and/or modeled FOS behavior. Conventional FOS interconnects have risetimes on the order of 500 ps to 1 ns. By using RLC networks of resistors, capacitors and inductors along with reduced FOS lengths, risetimes on the order of 100 ps are possible. However, risetimes on the order of 100 ps are insufficient to achieve write current bandwidths required for recording frequencies greater than 3 GHz (6 Gbit/sec).
As disclosed in Generation of ultrashort electrical pulses with variable pulse widths, Keil, U. D., et al., Appl. Phys. Lett., 1995 66(13) p. 1629, semiconductor substrates subjected to femtosecond solid state laser pulses can generate THz radiation with risetimes on the order of 400 fs. As disclosed in 375-GHz-bandwidth photoconductive detector, Chen, Y., et al., Appl. Phys. Lett., 1991 59(16) p. 1984, photoconductive substrates have been used to generate voltage pulses as large as 6V from a 30 Ohm switch having a full-width-half-maximum pulse width of 1.5 ps. The magnetic recording industry could greatly benefit from incorporating photoconductive current sources capable of producing such signals adjacent a recording head in a magnetic recording head assembly in order to extend data rates beyond 6 Gbit/sec.
Accordingly, there is identified a need for an improved recording head for higher recording densities and increased data rate transmission that overcomes limitations, disadvantages or shortcomings of known recording heads.